The aim of this research project is to study mainly on the electron microscopic level, the formation and growth of optic fibers from the retina to the tectum in the chick. In addition, data are being gathered by use of the whole mount silver - pyridine stain of Goldberg In embryonic chicks between 2 days and hatching, the developing optic pathway will be studied at the following sites: (1) retina, including the optic fissure, (2) several regions along the optic nerve and tract, (3) optic chiasm, (4) tectal surface, and (5) terminal connections in the tectum. Specific aims are to determine if: (1) optic fibers are grouped into fascicles on the basis of common factors such as size of axons or spatial origin, (2) any mechanical forces are involved in directing the fibers into the optic fissure, across the chiasm and onto the tectal surface and (3) synapses are established on the first available site in the tectum or if there is simultaneous projection of optic fibers to various regions in the tectum.